Yuan Shujuan (Suifenhe Special Equipment Inspection and Research Institute, Suifenhe 157300, Heilongjiang) In welding construction, pipeline teaming and welding process are the main measures of welding quality, as well as the main way of affecting the speed and direction of medium flow in the pipeline The main way to control and analyze pipeline wear and safe operation problems. In the pressure pipeline, the general delivery media are flammable and explosive substances, so the installation quality requirements are the key to ensuring the normal and orderly development of society and the full play of the pipeline quality and function. For this reason, controlling the welding quality in pressure pipeline engineering is the focus of pipeline installation quality control. In this paper, combined with the analysis of various key construction points in the pressure pipeline welding construction, a reasonable and effective quality control method is proposed.
The pressure pipeline is one of the municipal special equipment, and it is the main foundation for conveying various special media in the current social development. Various media transported by pressure pipelines are often flammable and explosive, so various defects in the pipeline structure are reasonably controlled during construction. Welding is the main key link in the construction of current pressure pipelines. During the construction, various prone defects are strictly controlled to ensure the reasonable application of pressure pipeline quality.
In the welding of pressure pipelines, the welder must select the welder engaged in the pressure pipeline, and must have certain qualifications and construction experience. Only after passing various examinations can he engage in the corresponding welding work.
In the selection and preparation of welding equipment, arc welding with good welding advantages is generally used as the main welding method, and it is necessary to ensure a reasonable choice of welding power source. And to ensure the completeness and performance of the welding hot seam treatment device is stable and reliable.
Subject to the on-site conditions, heat treatment methods such as plasma arc should be used as much as possible. After the bevel processing is completed, the bevel must be removed, and the various problems and slag in the bevel must be removed, and the Factors, try to smooth the uneven areas around.
The pipeline joint organization should firstly reduce the quality requirements for the processing and treatment of hot grooves during the construction process, and deal with the various hidden quality problems in the pipeline joints in a reasonable manner to ensure the rationality and goodness of the application. The paired butt welding of the pipe joint is the key to ensure the welding quality and promote the good formation of the back of the pipe joint. If the groove form, the pairing gap, and the size of the blunt edge are not suitable, it is easy to cause defects such as indentation, weld nugget, and insufficient penetration. The pairing gap should be uniform, and the positioning should ensure that the inner wall of the receiving pipe is flush and the amount of misalignment of the inner wall does not exceed 10 ° /., And should not be greater than 15 mm. If the wall thickness is inconsistent, the grinding and transition should be carried out according to the regulations.
If the positioning plate is welded, it should be in the same direction of the fillet weld of the welded tube plate. The pipe fittings should be placed firmly when aligned, and measures should be taken to prevent deformation during the welding process. In tack welding, the same welding materials and welding process as the root bead should be used and welded by qualified welders.
The welding process control construction unit shall have a perfect material management system to ensure that the specifications and models of materials meet the design requirements. On-site materials: On-site materials staff check whether the name, specifications, model, quantity and quality certificate of the materials are consistent with things based on the arrival certificate. The qualified materials and on-site materials staff are responsible for the storage and registration. Sometimes the specifications of some materials on site are too large to be stored in the warehouse, so you should choose a suitable open space for storage and do a good job of protection. Materials that need to be stored in the warehouse must be properly stored in the warehouse to prevent loss and damage. When issuing materials, be sure to check the engineering items, specifications, models, materials and quantities of the materials to prevent errors.
3 Welding process evaluation and welding process Welding process evaluation coverage of various materials and welding joints in pipeline welding construction reaches 100% assessment. Welding technicians should formulate practical welding procedure guidelines based on the design drawings, relevant construction specifications and current standards, welding procedure evaluation and the actual conditions on the construction site. Perform technical briefing on welders and pipemen before construction, including welding materials, process parameters, preheating before welding, interlayer, postheating, temperature and time of heat treatment, storage, use and nondestructive testing of welding materials, etc. . The pipeline number should be marked on the welding process guideline. The pipelines of different processes are numbered separately. The pipelines with the same welding process can be written in a process guideline, indicating the pipeline code. To confirm the groove, size and assembly requirements (signature confirmation), the welder must strictly implement the welding process, and the on-site quality inspector should strengthen the supervision and inspection in this regard, which is the key to ensuring the welding quality. The welder should carry out the process handover, confirm the quality of the breach, and ensure the correct implementation of the welding process.
The number of repairs in the same part of the weld should not exceed two times. For the first and second repairs, the welding process personnel analyzes the causes of the defects required for repair and prepares the repair process. Welding responsible engineer and relevant personnel carefully analyze the reasons to determine the measures to avoid the occurrence of rework, and then prepare the rework process, which will be approved by the project technical person in charge or project quality assurance engineer. After the welding seam is repaired, welding inspection and non-destructive testing should be carried out according to the requirements of the repair process. Pipeline welds that require post-weld heat treatment should generally be reworked before heat treatment. For example, rework after heat treatment and repair welding should be followed by necessary heat treatment. For stainless steel welds with intergranular resistance requirements, the original requirements shall still be ensured in the repaired parts. The number, location and repair status of the weld repair shall be recorded in the handover data, and the records and reports of the repair shall be imported into the project file.
The inspection of the weld surface quality after welding shall be carried out before non-destructive testing and pressure test. Therefore, the surface quality of the weld should be 100% visually inspected using standard samples, gauges, hardness testers, etc. and meet the specific requirements of the GB50236-98 standard, and the results should be faithfully recorded.
The surface of standard welds with acceptable appearance shall not have defects such as cracks, pores, craters and slag inclusions, and shall not have slag and spatter. The undercut and weld height shall meet the relevant requirements.
5.2 Inspection of internal quality of welds The method and ratio of non-destructive testing shall comply with the relevant construction codes, standards and design requirements. When the RT method is used for random inspection, the welding seam of each welder shall be sampled according to the specified proportion. The fixed tube mouth shall not be less than one welded mouth. The welded mouth shall be jointly inspected by the construction unit and third-party supervisors Select and write down the welding port number. After the non-destructive testing is completed, the construction unit shall promptly mark the pipeline number, pipeline material, specifications, welding port location, welder code, non-destructive testing location and non-destructive testing method on the pipeline but the line drawing.
The final inspection and test can only be carried out after the inspection and test of the materials used in the pressure pipeline have been completed and qualified, and the process inspection and test of the installation process have been completed and qualified and the data are complete and meet the requirements.
5.3.1 After the installation of the pressure pipeline is completed, it can only be carried out after passing the joint inspection; 3.2 Strictly follow the inspection and test procedures and requirements, and make a record; 3.3 The pipeline that transports highly toxic, toxic and flammable fluids must determine the leakage according to the regulations; after the pressure test of the vacuum system pipeline, a vacuum test is also required.
With the current social development, people's demand for various materials has increased, and pressure pipes are the main transportation method for transporting various flammable and explosive materials. The quality requirements during construction are the main management and control basis. The quality control of the pressure pipeline is interlocking. Only during the construction process, the operation should be carried out carefully according to the relevant specifications to ensure that the operators are due diligence in the work. The work of seeking truth from facts is the basis for obtaining a good guarantee for the construction quality.
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